At right, Ruben Ramirez Cardenas, who is set to be executed. At left, Mexico’s Deputy Foreign Minister for North America Carlos Manuel Sada Solana speaks at a news conference about the case.

(AP/Reuters)

After two decades on death row, a Mexican national at the center of an international dispute is scheduled to be put to death by lethal injection Wednesday night in Texas unless the U.S. Supreme Court steps in an issues an 11th hour stay.

Lawyers for Ruben Ramirez Cardenas asked the nation’s highest court to halt the Texas execution, citing advances in DNA testing. Cardenas is set to die for the February 1997 rape and beating death of his 16-year-old cousin Mayra Laguna.

Cardenas told police he and his friend Jose Antonio Lopez Castillo were on drugs when they drove to Laguna’s apartment and raped her. When he untied his cousin she “came at me,” he said, scratching and kneeing him. He said he “lost it” and then started punching her in the face.

When he hit her in the neck, Laguna started to cough up blood. Cardenas tried to revive her. When that didn’t work, he tied her back up and “rolled her down a canal bank.”

It’s what happened next that has Mexican officials and human rights groups arguing he shouldn’t be put to death.

Cardenas’ defense team, funded by the Mexican government, claims the United States violated an international treaty by denying Cardenas the opportunity to speak to his country’s consulate after his arrest.

If Texas officials execute Cardenas, they would be in apparent violation of the Vienna Convention on Consular Relations.

In 2004, the U.N.’s international court in the Hague ruled that the U.S. must review cases similar to Cardenas’. Then-President George W. Bush told states to comply but the Supreme Court overruled him and said it was up to Congress – not the president – to order states to obey.

Since then, Congress has dragged its feet.

“The result: an illegal loophole states are exploiting to execute foreign nationals in violation of international law,” the ACLU says.

The U.N. high commissioner for human rights issued a statement Tuesday calling for the death sentence “to be annulled and for Mr. Cardenas to be re-tried in compliance with international standards relating to due process and fair trial.”

Kuykendall adds that the legality of the treaty was never in question and therefore should be followed.

“It’s not a question of whether there really is a binding legal obligation or not; every justice in the Supreme Court agrees that there is,” Kuykendall, who heads up the Mexican Capital Legal Assistance Program, said. “The only question is who is going to implement the legal mechanism to put it into place.”

Mexico, unlike the U.S., does not have capital punishment. The country hasn’t weighed in on whether Cardenas committed the crimes but instead has focused on the treaty.

Cardenas also reportedly was denied a lawyer for 11 days. His attorneys argue that the DNA evidence against him is faulty, his confession was coerced and their client is innocent.

But Rene Guerra, the former local district attorney who prosecuted Cardenas, dismissed the complaints.

“I never would have authorized a case that was not there or was a flimsy investigation,” he told The Associated Press. “This guy deserves the death penalty.”

With only hours until his scheduled execution, Cardenas attorneys filed two federal lawsuits seeking to stop Wednesday’s execution.

One argues that Cardenas’ due process and civil rights are being violated because state officials are refusing to release evidence that could lead to new DNA testing in the case.

The other asks for a phone in the prison so Cardenas’ attorney Maurie Levin can contact the Texas governor or the courts before and during the execution.

Cell phones are typically barred from Texas prisons. There are no landlines either.

If Cardenas is executed, he would be the 166th inmate to be executed in Texas in the past decade. He’d be the 11th Mexican national to be executed in the U.S. in 35 years.